Joining the un-joinable: New polymer linking technology based on nano crystals developed

Aug 27, 2012

Ever tried to paint on top of silicone? After a few hours, the paint will peel off. Annoying. Silicone is a so-called low surface energy polymer, well known from flexible baking forms: A synthetic material that has an extremely low adhesion or "stickiness". Teflon is similarly non-sticky and well known from frying pans. Researchers of Kiel University (Germany) have now developed the first technology which is capable of joining these two "unjoinable" materials. The technology applies passive nano-scaled crystal linkers as internal staples. The nano staples open up solutions to a large number of technical challenges, for example in medical engineering.

The work carried out within the DFG-funded Collaborative Research Center 677 "Function by Switching" was published today in the scientific journal Advanced Materials.

"If the nano staples make even extreme polymers like Teflon and silicone stick to each other, they can join all kinds of other plastic materials", says Professor Rainer Adelung. Adelung is leading the functional nano materials group at the Institute of Materials Science in Kiel and lead the research project from the materials science side. The new technology of joining materials without chemical modifications can be used, according to Adelung, in a variety of everyday life and high tech applications. The technique is easy to use and does not need expensive equipment or material.

The tetrapod nano staples sink into the polymer, while some of the arms are sticking out. Image from scanning electron microscope. Copyright: CAU, Image: Xin Jin

The linkers are micro and nano scaled crystals made of zinc oxide. They are shaped like tetrapods, where four legs protrude from the point of origin. Large-scale tetrapods are known for their ability to interlock and form strong bonds, for example in coastal protection.

During the joining process, the zinc oxide crystals are sprinkled evenly onto a heated layer of Teflon. Then, a layer of silicone is poured on top. In order to join the materials firmly, they are then heated to 100°Celsius for less than an hour. "It's like stapling two non-sticky materials from the inside with the crystals: When they are heated up, the nano tetrapods in between the polymer layers pierce the materials, sink into them, and get anchored", explains Xin Jin, the first author of the publication, who is currently working on her PhD thesis. Her colleague and supervisor, Dr. Yogendra Kumar Mishra, explains the adhesive principle: "If you try to pull out a tetrapod on one arm from a polymer layer, the shape of the tetrapod will simply cause three arms to dig in deeper and to hold on even firmer."

The two polymer layers are stapled from the inside using nano crystals made of zink oxide. Conceptional drawing. Copyright: CAU, Image: Jan Strüben

In high technology businesses such as medical engineering, there is a strong demand for innovative ways to make polymers, particularly silicone, stick to other materials, for example to further develop breathing masks, implants or sensors. Medical applications require materials that are absolutely non-harmful, i.e. biocompatible. Many joining methods involve chemical reactions, which may change the polymers' properties and can cause injurious or even toxic effects on organisms. The tetrapod stapling, on the contrary, is a purely mechanical process. Therefore the Kiel team assumes it to be biocompatible.

With the tetrapod staples, the scientists have achieved a stickiness—the so-called peel strength—of 200 Newtons per meter, which is similar to peeling sticky tape off glass. "The stickiness we have achieved with the nano tetrapods is remarkable, because as far as we could verify, no one has ever made silicone and Teflon stick to each other at all", says co-author Lars Heepe, PhD student from the Zoological Institute of Kiel University, who precisely measured the adhesion and described what the stapled material looks like on the microscopic scale. "Measuring adhesion quantitatively is not as easy as it looks, precise experiments have to be carried out in order to prove the function of the linkers and rule out all errors", says Professor Stanislav Gorb, leading the group Functional Morphology and Biomechanics.

A team headed by Dr. Naoe Hosoda at the National Institute for Materials Science is engaged in research and development of "Future joining technology for reversible interconnection" as an environment-friendly ...

(PhysOrg.com) -- Researchers at Northeast Normal University in China, have come up with a three-step process that when applied to cotton material results in a fabric that is both waterproof and very highly ...

A new review published in WIREs Nanomedicine and Nanobiotechnology explores how nanotechnology may be used to develop safer breast implants as an alternative to silicone rubber, minimizing health complications.

Polymer nano-films and nano-composites are used in a wide variety of applications from food packaging to sports equipment to automotive and aerospace applications. Thermal analysis is routinely used to analyze ...

Thermoelectric materials can be assembled into units, which can transform the thermal difference to electrical energy or vice versa – electrical current to cooling. An effective utilization requires however that the material ...

Recommended for you

Cellulose nanocrystals derived from industrial byproducts have been shown to increase the strength of concrete, representing a potential renewable additive to improve the ubiquitous construction material.

Scientists at Japan's Kyushu University say polymer-wrapped carbon nanotubes hold much promise in biotechnology and energy applications. The paper was recently published in Science and Technology of Advanced Ma ...

Swiss scientists from ETH Zurich have developed a thermometer that is at least 100 times more sensitive than previous temperature sensors. It consists of a bio-synthetic hybrid material of tobacco cells and nanotubes.

From smartphones and tablets to computer monitors and interactive TV screens, electronic displays are everywhere. As the demand for instant, constant communication grows, so too does the urgency for more ...

An unusual and very exciting form of carbon - that can be created by drawing on paper- looks to hold the key to real-time, high throughput DNA sequencing, a technique that would revolutionise medical research ...

Nanoparticles are specifically adapted to the particular application by Small Molecule Surface Modification (SMSM). Thereby surfaces of workpieces or mouldings are expected to exhibit several different functions at one and ...

User comments : 0

Please sign in to add a comment.
Registration is free, and takes less than a minute.
Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.